A conventional sensor device such as an acceleration sensor and/or an angular speed sensor includes a circuit chip with a bonding portion, a sensor chip stacked on the bonding portion of the circuit chip, and a film-type adhesive interposed between the circuit chip and the sensor chip.
In this type of conventional sensor device, a stack structure that mounts the sensor chip on top of the circuit chip is adopted in order to reduce manufacturing costs by minimizing an implementation size.
The adhesive that bonds an upper surface of the circuit chip and a lower surface of the sensor chip is a film-type polyimide adhesive containing an inorganic filler such as BN (boron nitride) or Ag (silver).
The film-type adhesive including filler is used to maintain both the binding strength of the circuit chip and the sensor chip, and the elasticity of the adhesive when the sensor is put in a high temperature environment.
However, the sensor chip attached on the circuit chip with the film-type adhesive including filler has the following problems according to a study conducted by the inventors of the present invention.
The film-type adhesive including a high density filler, e.g. approximately 10 weight %, tends to have lumps in the filler caused by cohesion. As a result, the lower side of the sensor chip damages the circuit chip by pressing the lumps in the filler against the surface of the circuit chip when the sensor chip is pressed against the circuit chip to be bonded thereto. The damage caused by the process may result in a decreased performance and malfunction of the circuit chip.